Short Communication: Composition of Milk Protein and Milk Fatty Acids Is Stable for Cows Differing in Genetic Merit for Milk Production

Changing the composition of milk protein and of milk fatty acids alters nutritional and physical properties of dairy products and their consumer appeal. Genetic selection for milk yield decreases concentrations of milk protein and of milk fat. Little is known, however, about how the decrease affects...

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Bibliographic Details
Published in:Journal of dairy science 2007-08, Vol.90 (8), p.3955-3960
Main Authors: Bobe, G, Lindberg, G.L, Freeman, A.E, Beitz, D.C
Format: Article
Language:English
Subjects:
Animal Feed - analysis
Animal productions
Animals
Biological and medical sciences
breeding value
Caseins - analysis
Cattle - genetics
Cattle - physiology
dairy cows
dairy protein
fatty acids
Fatty Acids - analysis
Female
Food industries
Fundamental and applied biological sciences. Psychology
genetic merit
genetic techniques and protocols
Lactation - genetics
Least-Squares Analysis
Male
milk
Milk - chemistry
Milk - secretion
milk analysis
Milk and cheese industries. Ice creams
milk composition
Milk Proteins - analysis
milk yield
selection criteria
Selection, Genetic
Terrestrial animal productions
Vertebrates
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Summary:Changing the composition of milk protein and of milk fatty acids alters nutritional and physical properties of dairy products and their consumer appeal. Genetic selection for milk yield decreases concentrations of milk protein and of milk fat. Little is known, however, about how the decrease affects composition of milk protein and milk fatty acids. The objective of this study was to quantify changes in composition of milk protein and of milk fatty acids in cows differing in genetic merit for milk production. Three measures of genetic merit for milk production were used for each cow: genetic line, parent average predicted transmitting ability (PTA) for milk, and cow milk PTA. Composition of milk protein and milk fatty acids were compared in 448 milk samples from 178 cows representing 2 divergent lines of Holsteins that were bred for high or average PTA for milk and combined milk protein and fat yield. High-line cows (n = 97) produced more milk that contained less fat and had higher proportions of αS₁-casein in milk protein than did average-line cows (n = 81). We additionally obtained from 233 cows (178 cows representing the 2 genetic lines and 55 cows with ancestors from both genetic lines) the parent average milk PTA and cow milk PTA and compared composition of milk protein and of milk fatty acids in 592 milk samples. Cows whose parent average milk PTA was above or equal to the median of the 233 cows produced more milk that contained less protein and less fat and that tended to have greater proportions of αS₁-casein in milk protein than cows whose average milk PTA was below the median. Similarly, cows with above or equal median milk PTA of the 233 cows produced more milk that contained less protein and less fat and had greater proportions of αS₁- casein in milk protein than did cows with below-median milk PTA. Milk fatty acid composition was not consistently different between groups. Therefore, selection for milk yield decreased concentrations of milk protein and milk fat but had little effect on composition of milk protein and milk fatty acids.
ISSN:0022-0302
1525-3198
DOI:10.3168/jds.2007-0099